Determining the actual class of an object

Hi,

How can I determine the actual class an object? For example: 

var oRoot = Scene.getSelectedNode(1).getSkeleton();
var numProps = oRoot.getNumProperties();

var oProp;
for(var i = 0; i < numProps; ++i)
{
   oProp = oRoot.getProperty(i);

   // determine the class of current oProp
   ???
}

I've tried "typeof" and "oProp.__proto__" and all returns "Object". How can I determine which subclass of DzProperty oProp actually is?

Thanks